1. Field of the Invention
This invention relates to a television tuner with fine tuning means and, more particularly, to a mechanism for operating fine tuning means in television tuners.
2. Description of the Prior Art
Conventionally, in television tuners having an operating shaft for channel salection, there has been provided fine tuning means including a bobbin having a coil around the outside thereof, and a plunger having at one end a ferromagnetic core. In order to effect fine tuning, it is essintial that the core is moved to a desired position within the bobbin so that the inductance of coil is varied. Such fine tuning means is generally operated by a mechanism comprising a sleeve rotatably disposed around the operating shaft, and a cam adapted to move the plunger axially with the rotation of the sleeve. However, the conventional mechanism for operating fine tuning means is very complicated in construction since the cam is driven through power transmission means such as, for example, a pair of gears. Because of the complex construction, the mechanism wears and the parts are reduced in size after prolonged use, resulting in the dislocation of the parts. Further, the conventional mechanism has the disadvantage that the core may be shifted from the desired position when any mechanical shock is applied to the tuner.